An apparatus is known for simultaneously treating a plurality of samples by means of a liquid, the apparatus comprising a plurality of sample-carrier baskets driven helically about a vertical axis in respective vessels filled with said liquid and maintained at a desired treatment temperature by a water bath.
At the end of treatment by said liquid, the sample-carrier baskets are withdrawn from the vessels and are placed in an oven to dry the samples.
Such apparatus does not give complete satisfaction, particularly since it requires laboratory personnel to perform a large amount of handling, thereby limiting the number of experiments that can be performed in a given length of time.
Also, when it is desired to determine the effect of a hair treatment substance on hair, it is important for tests to be performed on the samples in a manner that is as representative as possible of the real action of the substance on hair of the head, which depends in particular on the conditions under which the substance is applied to the head, and the various actions performed before or after the substance is applied, e.g. shampooing and drying.